Grant Summary Approximately 1.6 million patients are transferred between hospitals yearly, experience a disproportionately high mortality, and cost in excess of $100 billion yearly. Inter-hospital transfers are a representative high risk transition of care that occurs across disparate health care systems wherein health information systems often do not effectively share data. Frequent breakdowns in information handling make this population particularly vulnerable to errors. Improving inter-operability of electronic health records (EHR) such as through adoption of regional Health Information Exchanges (HIE) has the potential to facilitate care coordination throughout the transfer process and improve patient outcomes. The overarching objective of this application are to demonstrate at the population and patient level that interoperability improves mortality and care efficiency. Over the 4 years of the proposed study we will accomplish this goal across 3 complimentary aims: Aim 1: We will perform a large population study linking hospital participation of a health information exchange to outcomes and cost of care following an inter hospital transfer. Aim 2: We will complete an interventional study interventional studies that improves the usability available data sharing tools and determine the impact on patient safety and outcomes. Aim 3: We will investigate the impact of the seamless integration of two EHR systems following the merger of two hospital systems which frequently transfer patients. This project will provide valuable information for both policy makers and hospital administrators as they design interventions to improve EHR interoperability. Additionally, this study will inform best practices on how to coordinate the care of a patent transferred between hospitals and directly improve outcomes.